React Questions

March 16, 2023

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Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

Deprecated: trim(): Passing null to parameter #1 ($string) of type string is deprecated in /home/u797631661/domains/codermantra.com/public_html/wp-includes/formatting.php on line 449

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React Questions

1 / 15

1. What function allows you to render React content in an HTML page?

A. React.mount()

B. ReactDOM.start()

C. ReactDOM.render()

D. React.render()

2 / 15

2. What happens when the following render() method executes?

render(){
   let langs = ["PHP","ES6","JAVA"]
     return ( < div>
       {langs.map(it =>  < p > {it}  < /p > )}
      < /div > )
 }

A. Error:cannot use direct javascript code in jsx

B. error:should be replaced with a for..loop fo correct output

C. display the list of language in the array

D. displays nothing

3 / 15

3. What is the difference between the click behaviors of these two buttons (assuming that this.handleClick is bound correctly)?

A. < button onClick={this.handleClick} > Click Me < /button >  < /code> < /pre >


B. < button onClick={event => this.handleClick(event)}> Click Me < /button >

A. Button A will not have access to the event object on click of the button.

B. Button B will not fire the handler this.handleClick successfully.

C. Button A will not fire the handler this.handleClick successfully.

D. There is no difference

4 / 15

4. What is the default local host port that a React development server uses?

A. 3000

B. 3500

C. 5000

D. 8080

5 / 15

5. How can you combine the following arrays using the spread operator?

A. const combined = [array1, array2];

B. const combined = …array1 + …array2;

C. const combined = […array1, …array2];

D. const combined = array1 + array2;

6 / 15

6. What do you call a React component that catches JavaScript errors anywhere in the child component tree?

A. error bosses

B. error catchers

C. error helper

D. error boundaries

7 / 15

7. When rendering a list using the JavaScript map() method, what is required for each element rendered?

A. id

B. key

C. data

D. index

8 / 15

8. Which of the following is method is not a part of ReactDOM?

A. ReactDOM.hydrate()

B. ReactDOM.destroy()

C. ReactDOM.createPortal()

D. All of the mentioned

9 / 15

9. What are the limitations of ReactJS?

A. React is only for view layer of the app so we still need the help of other technologies to get a complete tooling set for development

B. React is using inline templating and JSX. This can seem awkward to some developers

C. The library of react is too large

D. All of these

10 / 15

10. As soon as the state of react component is changed, component will

A. Does nothing,you have to call render method to render the component again

B. re-render the component

C. be created again from scratch

D. none of these

11 / 15

11. What is the children prop?

A. A property that lets you pass data to child components

B. A property that lets you set an object as a property

C. A property that lets you nest components in other components

D. A property that adds child values to state

12 / 15

12. . What is the name of this component?

  class Clock extends React.Component {
  render() {
    return < h1 >  Look at the time: {time} < /h1>  ;
  }
}

A. Clock

B. It does not have a name prop.

C. React.Component

D. Component

13 / 15

13. How many ways of defining your variables in ES6?

A. 3

B. 1

C. 4

D. 2

14 / 15

14. Which of the following is used in React.js to increase performance?

A. Virtual Dom

B. Original Dom

C. Both A And b

D. None of all

15 / 15

15. What will be the output of the following code?

import React, { Component } from 'react';  
const App = () => {  
    
      return(  
          < div >  
             < h1 className = "hello" > {25+20}< /h1 >   
          < /div >  
      );   
}  
export default App;

A. 25

B. 45

C. 35

D. none of these

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The average score is 41%

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